A conventional semiconductor manufacturing process includes forming an insulation layer and a conductive layer on a substrate, a photolithographic process, etc. The photolithographic process comprises forming a photoresist pattern on an underlying layer to be patterned, etching the layer exposed by the photoresist pattern, and then removing the photoresist pattern. In addition, organic materials or polymer may occur from the reaction between the underlying layer to be etched and an etching gas. Conventionally, the photoresist pattern and organic materials or the polymer are removed by an oxygen plasma ashing and a sulfuric strip process.
Operation speed of the devices has a close relationship with the resistances of the source/drain regions. Therefore, to increase the operation speed of a device, a metal silicidation process is used for forming semiconductor devices. The silicidation process comprises forming a cobalt silicide layer having resistivity lower than that of silicon from a reaction between cobalt and silicon at a predetermined temperature. In the silicidation process, non-reacting cobalt should be removed without removing the cobalt silicide layer.
Moreover, in a conventional cobalt silicidation process, a titanium nitride layer is formed so as to prevent oxidation of cobalt and agglomeration of the silicide layer in the silicidation process. Therefore, a titanium nitride layer should be removed after formation of the silicide layer.
If the layers are not removed, the layers can serve as contaminant sources and can cause electric short with neighboring conductors.
Conventionally, in the silicidation process, the non-reacting metal layers and the titanium nitride layers are removed by a mixture solution including peroxide (H2O2), i.e., a strong oxidation agent.
Meanwhile, as the semiconductor devices are highly integrated in an economic point of view, a conventional polysilicon gate electrode cannot satisfy the needs of the proper operation speed and the characteristic of a sheet resistance of the gate electrode. Therefore, a metal layer such as a tungsten layer, which has resistivity lower than a polysilicon layer, is stacked on the polysilicon gate electrode to form a metal gate electrode. Therefore, the low resistivity tungsten gate should also not be etched (or removed). In addition, a metal interconnection with tungsten (e.g., a word line or a bit line) should not be etched by the cleaning solution.
On the contrary, the peroxide, which is conventionally used in the silicidation process, etches the tungsten. Thus, the high-speed devices cannot be embodied using the conventional peroxide.
Accordingly, as the need of high-speed devices increases, the need for a new cleaning solution that can selectively remove metal layers such as a titanium nitride layer and a cobalt layer without removing metal layers such a cobalt silicide layer or a tungsten layer also increases.